1. Field of the Invention
The present invention relates to a liquid crystal display capable of displaying an image by a light reflection mode and a light transmission mode.
2. Description of the Related Art
It was sufficient for the conventional display of portable equipment such as a portable telephone or a pager to be capable of displaying simple characters such as numerals and letters. However, in accordance with the drastic development in the IT technologies achieved in recent years, it is desirable for a small, light and thin display having a low power consumption and capable of displaying a high quality color image to be put to a practical use even in the field of portable equipment, particularly, a portable information terminal.
As a display meeting the requirement noted above, a reflection type liquid crystal display, for example, is considered hopeful and has already been put partly to a practical use. When used outdoors in the daytime, the reflection type liquid crystal display is capable of displaying an image that is visible easily. However, a light source is not included in the reflection type liquid crystal display, with the result that the image displayed in a dark place can be scarcely recognized. In other words, the reflection type liquid crystal display is limited by the environment of use.
As a countermeasure, proposed is a front light technology. In the front light technology, the display surface of the reflection type liquid crystal display is covered with a transparent planar light source so as to make up for the insufficient illuminance of the external light. In this technology, it is unnecessary to change the internal structure of the liquid crystal display. However, the quality of the image is lowered by the reduction in the amount of reflected light, the blurring of the image, the increase in the feeling of thickness (or depth), etc.
Jpn. Pat. Appln. KOKAI Publication No. 11-316382 discloses a liquid crystal display capable of displaying an image by utilizing both the light reflection and the light transmission modes. In the liquid crystal display, each of the pixel electrodes is formed by the combination of a light reflecting conductive film and a light transmitting conductive film. According to the liquid crystal display of the particular construction, an image is displayed by light reflection mode under an environment of high illuminance, and a backlight is lit under an environment of low illuminance to display an image by both light reflection mode and light transmission mode.
The liquid crystal display referred to above, which utilizes the light reflection mode and the light transmission mode in combination, permits displaying an image that can be recognized satisfactorily without depending on the illuminance of the external light. However, the light reflecting conductive film and the light transmitting conductive film, which are included in the particular liquid crystal display, are formed by independent processes so as to lower the yield and to increase the manufacturing cost of the liquid crystal display. In addition, it is necessary to superpose the light reflecting conductive film and the light transmitting conductive film one upon the other in the liquid crystal display of the particular construction, with the result that a marked reduction in reflectance is derived from the overlapping of these conductive films so as to make it difficult to obtain a bright image. Further, in the liquid crystal display utilizing the light reflection mode and the light transmission mode in combination, while certainly low in its power consumption compared with the liquid crystal display of the light transmission mode, the power consumption is not necessarily lowered sufficiently.
An object of the present invention is to provide a liquid crystal display capable of displaying a highly visible image without depending on the environment of use and also capable of further suppressing the power consumption.
According to a first aspect of the present invention, there is provided a liquid crystal display, comprising first and second substrates facing each other, first pixel electrodes arrayed on a first area within a surface of the first substrate facing the second substrate, second pixel electrodes arrayed on a second area within the surface of the first substrate facing the second substrate, the second area being different from the first area, a first common electrode supported by the second substrate and facing first pixel electrodes, a second common electrode supported by the second substrate and facing the second pixel electrodes, and a liquid crystal layer interposed between the first pixel electrodes and the first common electrode and between the second pixel electrodes and the second common electrode, wherein a first display region corresponding to the first area displays an image by light reflection mode, and a second display region corresponding to the second area can display an image by light transmission mode.
According to a second aspect of the present invention, there is provided a liquid crystal display, comprising first and second substrates facing each other, first pixel electrodes arrayed on a first area within a surface of the first substrate facing the second substrate, second pixel electrodes arrayed on a second area within the surface of the first substrate facing the second substrate, the second area being different from the first area, a first common electrode supported by the second substrate and facing the first pixel electrodes, a second common electrode supported by the second substrate and facing the second pixel electrodes, and a liquid crystal layer interposed between the first pixel electrodes and the first common electrode and between the second pixel electrodes and the second common electrode, wherein each of the first pixel electrodes is formed of a reflecting conductive film, and each of the second pixel electrodes is formed of a reflecting conductive film provided with at least one opening.
According to a third aspect of the present invention, there is provided a liquid crystal display, comprising first and second substrates facing each other, first pixel electrodes arrayed on a first area within a surface of the first substrate facing the second substrate, a reflecting film interposed between the first pixel electrodes and the first substrate, second pixel electrodes arrayed on a second area within the surface of the first substrate facing the second substrate, the second area being different from the first area, a first common electrode supported by the second substrate and facing the first pixel electrodes, a second common electrode supported by the second substrate and facing the second pixel electrodes, and a liquid crystal layer interposed between the first pixel electrodes and the first common electrode and between the second pixel electrodes and the second common electrode, wherein each of the first pixel electrodes and the second pixel electrodes is formed of a transparent conductive film.
Incidentally, the light reflection mode denotes a display mode utilizing external light incident on the side of the display surface or light emitted from a front light without utilizing the light source arranged on the side of the non-display surface. On the other hand, the light transmission mode denotes a display mode, which is low in the utilization rate of external light or light emitted from the front light compared with the light reflection mode and which utilizes light emitted from a light source arranged on the side of the non-display surface. In other words, the light transmission mode includes both the mode for performing the display by utilizing the light source alone arranged on the side of the non-display surface and the mode (light reflection-transmission combination mode) for performing the display by utilizing both light emitted from the light source arranged on the side of the non-display surface and light on the side of the display surface source (external light and/or front light).
In the liquid crystal display according to each of the first and third aspects of the present invention, an image can be displayed by the light reflection mode in the first display region corresponding to the first area, and an image can be displayed by the light transmission mode in the second display region corresponding to the second area.
In the liquid crystal display according to each of the first and second aspects of the present invention, an image can be displayed by the light reflection mode in the first display region corresponding to the first area, and an image can be displayed by both the light reflection mode and the light transmission mode in the second display region corresponding to the second area.
In the liquid crystal display according to the first aspect of the present invention, it is possible for each of the first pixel electrodes to be formed of a conductive film capable of reflecting the light, and it is possible for each of the second pixel electrodes to be formed of a conductive film capable of reflecting the light and provided with at least one opening. In this case, it is possible for a material of the first pixel electrodes to be the same as a material of the second pixel electrodes. Further, it is possible for a material of the first common electrode to be the same as a material of the second common electrode.
In the liquid crystal display according to the first aspect of the present invention, it is possible for each of the first pixel electrodes and the second pixel electrodes to be formed of a transparent conductive film. In this case, it is possible for the liquid crystal display to further comprise a reflecting layer interposed between each of the first pixel electrodes and the first substrate.
In the liquid crystal display according to each of the first to third aspects of the present invention, it is possible for the first common electrode and the second common electrode to be electrically connected to each other.
Further, it is possible for the liquid crystal display according to each of the first to third aspects of the present invention to further comprise a planar light source device configured to emit light from a side of the first substrate opposite to a side of the first substrate facing the second substrate toward the liquid crystal layer. In this case, it is desirable for the planar light source device to be configured to irradiate selectively the second display region among the first and second display regions with the light.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.